Belarus has denied allegations of large-scale torture in a secret service jail for political prisoners. The statement comes after a just-released former presidential candidate and a leading activist spoke to reporters about the alleged mistreatment of inmates.

The secret service of Belarus, known as the KGB, has strongly denied allegations of wrongdoing in its detention facility.

But former presidential candidate Ales Mikhalevich, who was released last Thursday, describes the prison as "a KGB concentration camp."

He says KGB forces made him stand naked in the freezing cold, deprived him of sleep, dragged him on the floor while handcuffed, kept him in an overcrowded cell, and interrogated him without a lawyer.

Offering more details, Mikhalevich explains one incident when he and all detainees in his prison cell were allegedly taken to a separate cold room where they were stripped down. He says KGB forces made them stand naked, spread eagle, with their "arms stretched against the walls for about 40 minutes."

Mikhalevich says he was released under the condition that he informs the KGB about other opposition politicians and that he keeps silent about the torture of detainees.

He explains that the KGB also used torture to pressure him to cooperate with them.

Mikhalevich says "people wearing camouflage uniforms and face masks dragged" him out of his prison cell, handcuffed him behind his back and pulled his arms so high that his face was "hitting the concrete floor" and his bones cracked. He says they used this method until he promised to cooperate with them.

The former presidential candidate claims he was held in a freshly painted room without ventilation.

Another activist, Natalya Radzina, editor of the opposition Charter-97 website, says she was summoned by police Tuesday after attempting to confirm Mikhalevich's claims in an interview.

She told Radio Free Europe/Radio Liberty that she heard commands given by guards to male inmates of the KGB pretrial detention center that "corroborate" what Mikhalevich told journalists.

The KGB says the allegations are untrue and, in their words, removed from reality.

Mikhalevich and some 25 other Belarusian opposition leaders face prison sentences of up to 15 years if convicted of involvement in massive demonstrations that followed the country's December presidential election.

He was arrested with several other presidential candidates on December 19, 2010, after protesting President Alexander Lukashenko's election to a fourth term in office in what the opposition says was a rigged vote.

Mr. Lukashenko, who has ruled Belarus practically unchallenged for 17 years, has called for the "maximum prosecution" of those who led protests against his rule.

The European Union, currently headed by Hungary, and the United States have announced fresh financial and travel sanctions against the Belarus government in response to what they view as a violent crackdown by authorities on dissent.

Neighboring Poland has warned Minsk that Mr. Lukashenko may face the same fate as presidents in Egypt and Tunisia, who were ousted in recent uprisings.